Studying methane and other trace species in the Mars atmosphere using a SOIR instrument R. Drummond (1), A.C. Vandaele (1), F. Daerden (1), E. Neefs (1), A. Mahieux (1), V. Wilquet (1), F. Montmessin (2,3), J.L. Bertaux (2,3), E. Marcq (2) (1) Belgian Institute for Space Aeronomy (IASB-BIRA), Ukkel, Belgium (2) LATMOS, Verrières-le-Buisson, France (3) IPSL, Université UVSQ, Guyancourt, France
Talk outline SOIR instrument description Results from VEX-SOIR in orbit around Venus Possible observations from a representative Mars orbit Martian atmospheric constituents within the SOIR spectral range Detection limits Ongoing improvements to SOIR Nadir capabilities Conclusion
SOIR Instrument Characteristics SOIR characteristics Wavelength range Wavenumber range Spectral sampling interval Resolving power [λ/δλ=υ/δυ] FOV Spectral resolution Spatial resolution (Δz at limb) Detector Power Mass Size Value or range 2.29 to 4.43 µm 2353 to 4310 cm -1 1 pixel = 0.1 cm -1 23200 to 43100 2 x 30 0.12 0.18cm -1 < 1 km 2D HgCdTe, 320x256 pixel matrix 17.8 W < 8 kg 414 x 254 x 210 mm 3
SOIR instrument description Baseplate Detector Support Structure
Example of results: orbit 341.1 order 149 (2/4)
CO vertical profiles 80 60 40 Latitude [ ] 20 0-20 -40-60 -80 0 5 10 15 20 Local solar time Latitudinal dependency Latitude 30-30 0-60 -90 0 6 12 18 24 LST 130 120 110 130 120 110 Orb359.1 0 Orb435.2 0 Orb452.1 1 Orb487.2 0 Orb811.1 0 Orb813.1 0 Model Altitude [km] 100 90 80 70 100 90 80 70 60 10 5 10 10 10 15 Density [molec/cm 3 ] 60 10-10 10-5 10 0 VMR [-] (VMR obtained from total density of VIRA model)
Aerosols: Retrieval technique Extinction profiles Transmittances Extinction : 110 Orbit 341.1 - Bin 1 β N ext = I N N i 1 ln dzi ext I β λ, 0 i= 1 dz N ( z) 105 100 With dz i the thickness of layer i I i the atmospheric intensity of layer I I 0 the full sun intensity β i the extinction of layer i Altitude [km] 95 90 85 80 75 70 Order 112-3.98 µm Order 130-3.43 µm Order 149-2.99 µm Order 190-2.35 µm 10-8 10-7 10-6 10-5 10-4 10-3 Extinction [km -1 ] V. Wilquet, et al., Preliminary characterization of the upper Venusian haze from UV to mid-ir by SPICAV/SOIR on Venus Express, J. Geophys. Research, 2009
Aerosols extinction profiles: Significant variations at high Northern latitudes 95 95 Altitude [km] 90 85 80 90 85 80 Day 1 (blue) (Orbit 482) Day 4 (green) (Orbit 485) Day 3 (red) (Orbit 484) 75 75 70 70 Day 6 (magenta) Day 5 (black) (Orbit 487) (Orbit 486) -4-3 -2 Extinction [km -1 10 ] -4 10-3 10-2 V. Wilquet, et al., Preliminary characterization of the upper Venusian haze from UV to mid-ir by SPICAV/SOIR on Venus Express, J. Geophys. Research, 2009
Solar Occultation Possibilities at Mars For ascending node starting at vernal equinox
1 Q Simulated observations - Methane R0 R1 R2 R3 1 Transmittance 0.99 0.98 0.97 Order 135 0.99 0.98 0.97 Order 136 0.96 0.96 0.95 0.95 0.94 3018 3020 3022 3024 3026 3028 3030 3032 3034 3036 3038 0.94 3045 3050 3055 3060 3065 1 0.99 0.98 R4 R5 R6 Order 137 0.97 0.96 0.95 S/N Full Spectrum CH4 1ppb H2O 200ppm CO2 95.3% 0.94 3065 3070 3075 3080 3085 Wavenumber (cm-1)
Simulated observations - Formaldehyde 1 1 0.99 0.98 Transmittance 0.97 0.96 0.95 0.94 0.93 0.92 S/N Full Spectrum H2O 200ppm H2CO 5ppb Order 121 2705 2710 2715 2720 2725 0.95 0.9 0.85 Order 124 2775 2780 2785 2790 2795 1 0.99 0.98 0.97 0.96 0.95 0.94 0.93 0.92 Order 125 2795 2800 2805 2810 2815 Wavenumber (cm-1) S/N Full Spectrum H2O 200ppm H2CO 5ppb
Simulated observations C 2 H 6 and HCl 1 1 0.99 0.99 0.98 0.98 Transmittance 0.97 0.96 0.95 S/N Full Spectrum C2H6 1ppb HCl 2ppb 0.97 0.96 0.95 0.94 0.94 Order 132 0.93 2950 2955 2960 2965 2970 2975 Wavenumber (cm-1) 0.93 Order 133 2975 2980 2985 2990 2995 Wavenumber (cm-1)
SOIR Detection Capabilities Species Scientific Objective Current Knowledge Detection limit Expected SOIR Advance CH 4 Identify sources 0-60ppb 0.1 ppb CH 4 abundance & improve maps CO 2 Profile density and T MGS up to ~50 km 1%, 1K (accuracy) Model assimilation, P, T profiles H 2 O Profile <300 ppm 10 ppb Photo-chemical loss investigations CO Profile 700-800 ppm 1 ppm Provide GCM model constraints HDO among others Profiling isotopic ratios 17 OCO; 18 OCO 13 CO 2 ; C 18 O 2 0.85 ppm 1% (accuracy) Provide profiles Aerosols Properties, extinction profiles TES measurement Provide profiles, GCM validation H 2 CO C 2 H 2 C 2 H 6 HCl OCS SO 2 Search for unidentified species <3.0 ppb <2.0 ppb <400 ppb <2.0 ppb 10 ppb 1.0 ppb 0.1ppb 1 ppb 0.1 ppb 1 ppb 10 ppb 0.1 ppm Provide profiles and mapping These values are for solar occultation
Ongoing Improvements Development of an AOTF with side lobe suppression New echelle grating using innovative aluminum processing techniques Integration of a new generation FPGA to act as interface between the spacecraft telecommand system and the SOIR instrument Faster transmission rate and higher data volume Optical redesign and signal optimization Study on cooling of the resized baseplate and other methods to increase SNR Overall increase of Technological Readiness Level (TRL) for future flight opportunities
Nadir simulations 4.15 x 10-8 Q R0 R1 4.2 x 10-8 4.1 4.05 4 Order 135 4.15 4.1 Radiance 3.95 3.9 4.05 Order 136 3.85 4 x 10-8 3020 3025 3030 3035 3040 3040 3045 3050 3055 3060 3065 4.25 4.2 4.15 4.1 4.05 4 Order 137 S/N Full Spectrum CH4 10ppb Solar spectrum 3065 3070 3075 3080 3085 Wavenumber (cm-1)
Nadir observations (450 ppm H 2 O) x 10-8 x 10-8 4.15 4.2 Radiance 4.1 4.05 4 3.95 3.9 3.85 3.8 Order 135 4.15 4.1 4.05 4 3.95 Order 136 3.75 3.9 3020 3025 3030 3035 3040 x 10-8 3040 3045 3050 3055 3060 3065 4.25 4.2 4.15 Order 137 4.1 4.05 4 3.95 3.9 S/N Full Spectrum CH4 10ppb Solar spectrum 3065 3070 3075 3080 3085 Wavenumber (cm-1)
Conclusions SOIR is a spaceflight-proven, easy-to-accommodate instrument that has the full support of Belgian Science Policy The SOIR instrument has already proven its capability to monitor routinely key components of the Venus atmosphere In the atmosphere of Mars, SOIR could accurately measure CH 4 abundance down to sub-ppb level and retrieve the vertical profile; detect hydrocarbon species and measure the HDO/H 2 O isotopic ratio from orbit SOIR is evolving towards a versatile version including NADIR. The mapping would be more efficient i.e. not restricted to solar occultation seasons